Apparatus for thickening pulps.



J. E. ROTHWELL.

APPARATUS FOR THICKENING PULPS.

APPLICATION FILED SEPT. 1a, 1913.

1,099,396. Patented June 9, 1914.

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UNTTED STATES PATENT OFFICE.

JOHN EDWARD ROTHWELL, 01E BUTTE, MONTANA, ASSIGNOB, TO COLORADO IRON WORKS COMPANY, OF DENVER, COLORADO, A. CORPORATION OF MAINE.

APPARATUS FOR THICKENING PULPS.

Specification of Letters Patent.

Application filed September 18, 1913.

Patented June 9, 1914.

Serial No. 790,531.

To all whom it may concern Be it known that I, J OI-IN EDWARD Ro'rn- WELL, a subject of the King of Great Britain, residing at Butte, Montana, have invented certain new and useful Improvements in Apparatus for Thickening Pulps, of which the following is a specification.

My invention relates to apparatus for thickening pulps, and consists in improved means for withdrawing the thickened prod not.

In heretofore existing apparatus for thickening pulps, of which I am aware, it is impossible to withdraw a. uniformly thick product, and thisdefect has a serious adverse infiuence on the subsequent treatment. To obtain a pulp of high density, depth is necessary, and it is customary to make the bottom of the thickening vessel in the form of an inverted cone, the pulp discharge being at the bottom. The solids, instead of flowing evenly down to the opening, adhere to the inner surface of the cone with great tenacity and build up in thickness until there is only a small central space in which the pulp continues moving to the point of discharge. This results in the settling eilicioncy of the cone being greatly reduced and in the loss of the value of the cone as. a storage vessel for thickened pulp; No agitating means has thus far been provided which does not have the effect of reducing the density of the pulp, and attempts to breakup the caked pulp result in the dislodged masses clogging the opening. Even with pulps which are of such a nature as to have a tendency to slide down the sides of the cone, such movement. is irregular, resulting in surges which greatly disturb the desired action and cause the pulp discharge to be very irregular in density. To overcome this defect and enable the withdrawal of a thick pulp of uniform density, I provide means whereby a circuit of circulating dense pulp is maintained within the cone, the withdrawal being from this circuit. At the same time considerable storage capacity is secured in the cone, a result very desirable but not heretofore attainable practically, for the reason set forth.

My invention comprises a hollow cylinder,

open top and bottom, suspended vertically within the thickeningvessel in such manner that the top is above the pulp level and the erated at a capacity in excess of that re quircd for the withdrawal of the desired amount of pulp and it is this excess, circulated' through the cylinder and air lift, which maintains the solids in motion and prevents the adhesion of thickened pulp to the sides of the tank.

Inorder that my invention may be readily understood by those skilled in the art, I have appended hereto a sheet of drawings in which the figure is a sectional elevation of an apparatus embodying my invention. In this, 1 is a settling tank, circular in plan with a cone bottom and to which the material to be operated upon is delivered through the launder 2. Centrally within this tank is a hollow cylinder 3, of such length and so sustained that its top will be i above the level of the material in the tank and its bottom submerged rather deeply. lVithin this cylinder is a pipe 4, the lower open end of which is close to the apex of the cone and whose upper end opens into a re ceptacle i5, situated above the cylinder. The pipe l, with the inner pipe 6, form an air lift adapted to raise the densest pulp from the apex of the cone to the receptacle 5. The receptacle 5 is provided with suitable outlets susceptible of adjustment, molasses gates for example, as shown at 7 and 8. At 9, is shown a launder encircling the upper edge of the tank for the purpose of catching the clear liquid which overflows, and 10 is an outlet in this launder.

In operation, a mixture of fine solids suspended in liquid is fed continuously to the tank 1, as by the launder 2, the solids subs siding-and the clear liquid overflowing the rim of the tank into the launder 9. The clear liquid thus collected is drawn from this launder through the opening 10 and is carried off by the launder 11. The air lift, formed by the pipes 4 and 6, continuously elevates the thickened pulp from the apex of the cone, delivering it into the receptacle 5, from which a part of it is continuously drawn for use through the outlet 7 into the launder 12.. The air lift is operated at a greater capacity than necessary to supply the amount withdrawn through 7, and the excess is returned to the interior of the cylinder through other openings, one of which is indicated at 8. By this means the thick pulp is kept in circulation and prevented from settling hard and the entire mass occupying the lower portion of the cone and the interior of the cylinder is maintained of a substantially uniform density. Fluctuations in the liquid content of the pulp withdrawn through 7 are avoided, subsequent treatment of the product is facilitated, and control of the operation made easy. In practice, the difference in level between the surface 14, of the pulp in the cylinder and the surface 15, of the liquid in the body of the tank forms an efficient index of the density of the pulp being withdrawn. The upper end of the air pipe 6 is connect-ed to the air supply by a hose 18, so that if it is desired to agitate the pulp in the lower part of thecone, the pipe 6 may 'be lowered till it is below the orificeof the pump column 4, when the escaping air will rise upward outside of the pipe 4. When the pipe 6 is again raised so that its end is within the pipe 4, the air rises through the latter and the combination operates as an air lift. In operation a quite dense pulp is carried in the cone to a point above the lower edge of the cylinder 3, and

practised in the cyanid process. In this a very essential condition to satisfactory operation is the ability to draw a thick pulp of uniform density from each of the decantation vessels.

My invention is susceptible of variation as to the form of the parts and nature of the elements used as means to accomplish the desiredends as well as to the kind of tank or other vessel to which it is applied, the essence of my invention residing in means for maintaining a thick pulp in such a state of motion as to prevent its thickening to an undesirable degree and to enable the withdrawal of a thick pulp of uniform density. Thus, :I contemplate raising the thick pulp from the apex of the cone to the receptacle 5 by any means suitable for handling the particular material operated upon, adiaphragm pump for example being preferable under certain conditions (as where an air lift would cause excessive foaming ,or where compressed air was not available).

WVhat I claim is: I

1. In combination a tank for thickening pulps, means for withdrawing the thickened pulp comprising a receptacle placed above the tank, a partition Within the tank, a pump for raising the thickened pulp from the bottom of the tank to the receptacle and outlets from the receptacle adapted to deliver a portion of the pulp for use and to return the excess to the interior of the partition.

2. In combination a tank for pulps, means for withdrawing the thickened pulp consisting in a receptacle placed above the tank, a partition within the tank, an air lift for raising the thickened pulp from the bottom of the tank to the receptacle and outlets from the receptacle adapted to de liver a portion of the pulp for use and to return the excess to the interior of the partition.

3. In combination a tank for thickening pulps, means for .withdrawing the thickened pulp consisting in a receptacle placed above the tank, a partition within the tank, an air lift with a vertically adjustable air pipe for raising the thickened pulp fromthe bottom of the tank to the receptacle and outlets from the receptacle adapted to degliver a portion of thepulpfor use and to return the excess to the interior of thepartistion. the quiet settling conditions of the upper 4. In combination a tank for thickening.

.pulps, means for withdrawing the thickened pulp consisting in a receptacle placed above the tank, a partition within the tank, a pump for raising the thickened pulp from the bottom of the tank to the receptacle and adjustable outlets from the receptacle adapted to deliver a portion of the pulp for use and to return the excess to the interior-of the partition.

5.'In combination a tank for thickening pulps, means for withdrawing the thickened pulp consisting in a receptacle placed above the tank, apartition within the tank, an'air lift for raising the thickened pulp'from the bottom of the tank to the receptacle and adjustable outlets from'the receptacle adapted to deliver a portion of the pulp foruse and to return the excess to the interior of the partition,

6. In combination a tank for thickening thickening .l V

pulps, means'for withdrawing the thickened V .raising the thickened pulp from the bottom of the tank to the receptacle and adjustable outlets from the receptacle adapted to deliver a portion of the pulp for use and to return the excess to the interior of the partition.

7. In apparatus of the class described, a tank, a receptacle above the tank, a pump adapted to raise thick pulp from the bottom of the tank to the receptacle, one or more outlets in the receptacle for Withdrawing a portion of said pulp andmeans for returningthe excess pulp to the tank at a point near the bottom.

8. In apparatus of the class described, a tank, a receptacle above the tank, an air lift adapted to raise thick pulp from the bottom of the tank to the receptacle, one or more outlets in the receptacle for Withdrawing a portion of said pulp and means for returning the excess pulp to the tank at a point near the bottom.

9. In apparatus of the class described, a tank, a receptacle above the tank an air lift with a vertically adjustable air plpe ada ted to raise thick pulp from the bottom 0 the tank to the receptacle, one or more outlets in the receptacle for Withdrawing a portion of said pulp and means for returning the excess pulp to the tank at a point near the bottom.

In testimony whereof, I affix my signature in presence of two Witnesses.

JOHN EDWARD ROTI-IWELL.

Witnesses CARL J. TRAUERMAN, C. G. Ro'rHwELL.

flopiel of this patent may be obtained for live cents each, by addressing the Commissioner of Patents. Washington, D. 0.? 

